>As presented in Wright's grammar -- I'm looking at it now -- the
>Gothic vowels (using a circumflex in place of Wright's macron)
>and diphthongs are as follows, following §12:

What basis is there *really* for supposing the
ai ái aí and au áu aú distinction apart from
etymology? AFAIK there is no internal evidence
for any actually diphthongal ái or áu in 4th-6th
century Gothic, like occasional misspellings
with <aj> or <aw>. As for length it is of course
not at all expressed in Gothic orthography, but
must be inferred from etymology.